Aerobic granular sludge can successfully be cultivated in a sequencing batch reactor (SBR) treating dairy wastewater. Attention has to be paid to the fact that suspended solids are always present in the effluent of aerobic granular sludge reactors, making a post-treatment step necessary. Sufficient post-treatment can be achieved through a sedimentation process with a hydraulic retention time of 15-30 min. After complete granulation and the separation of biomass from the effluent, removal efficiencies of 90% CODtotal, 80% Ntotal and 67% Ptotal can be achieved at a volumetric exchange ratio of 50% and a cycle duration of 8 h. Effluent values stabilize at around 125 mg l-1 CODdissolved. The maximum applicable loading rate is nevertheless limited, as the stability of aerobic granules very much depends on the presence of distinct feast and famine conditions and the degradation of real wastewaters shows slower kinetics compared with synthetic wastewaters. As loading rate and volumetric exchange ratio are coupled in an SBR system, the potential of granular sludge for improving process efficiency is also limited.

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RESUMOEste trabalho estuda o potencial de aproveitamento energético dos subprodutos biogás e lodo gerados na estação de tratamento de efluentes (ETE) Laboreaux em Itabira (MG), composta de reatores UASB, filtros biológicos percoladores e unidade de desaguamento do lodo por filtro prensa. Os subprodutos biogás e lodo foram caracterizados em termos quantitativos (produção) e qualitativos (composição e poder calorífico) durante 12 meses de monitoramento. Foram estudados dois cenários de aproveitamento energético dos subprodutos: (i) uso prioritário do biogás para a secagem térmica do lodo e o excedente de biogás para geração de eletricidade em motor de combustão interna; e (ii) uso prioritário do biogás visando à geração de eletricidade e ao aproveitamento do calor dos gases de exaustão para a secagem térmica de lodo. Para a análise desses cenários, utilizou-se o software CHEMCAD® a fim de determinar as condições de queima do biogás em câmara de combustão e em motor de combustão interna, assim como na determinação dos balanços de massa e energia. O estudo analisou o potencial de aproveitamento dos subprodutos do tratamento como fonte de energia renovável para uso na própria ETE e para fornecimento a terceiros. No cenário 1, a geração de eletricidade é menor (atendendo 22,2% da demanda de energia da ETE), mas a secagem térmica possibilita maior redução no volume final de lodo a ser disposto ou a eliminação completa de disposição final se o lodo seco final (com 10% de umidade) for utilizado como combustível por terceiros. No cenário 2, a geração de eletricidade é capaz de suprir 57, 6% da demanda de energia da ETE, todavia o calor contido nos gases de exaustão não é suficiente para a secagem de todo o lodo desaguado, configurando uma menor redução na quantidade de lodo a ser disposto (13,5 ou 24, 9% de redução em massa, conforme a alternativa de remoção de umidade selecionada). ABSTRACTThis work assesses the potential of energy recovery of the byproducts biogas and sludge produced at the Laboreaux wastewater treatment plant (WWTP), in Itabira (MG), which is integrated by UASB reactors, trickling filters and sludge dehydration unit (filter press). The byproducts biogas and sludge were quantitatively (production) and qualitatively (composition and calorific value) characterized during a monitoring period of 12 months. Two scenarios for energy recovery from the byproducts were considered: (i) priority use of biogas for sludge thermal drying and the excess of biogas being used for power generation in an internal combustion engine (ICE); and (ii) primary use of biogas for power generation and the heat of the engine exhaustion gases being used for sludge thermal drying. Biogas burning conditions into a combustion chamber and in an internal combustion engine, as well as mass and energy balances for each scenario, were assessed with the CHEMCAD® software. The study analysed the potential use of the byproducts as sources of renewable energy for use in the WWTP itself and to be offered to third party. In scenario 1, the elect...

31This work assesses the potential of using energy from the biogas and sludge generated in 32 UASB reactors at the Laboreaux Sewage Treatment Plant (STP). Two scenarios were 33 considered: (i) priority use of biogas for the thermal drying of dehydrated sludge and the use 34 of the excess biogas for electricity generation in an internal combustion engine (ICE); and (ii) 35 priority use of biogas for electricity generation and the use of the heat of the engine exhaust 36 gases for the thermal drying of the sludge. Scenario 1 showed that the electricity generated is 37 able to supply 22.2% of the STP power demand, but the thermal drying process enables a 38 greater reduction or even elimination of the final volume of sludge to be disposed of. In 39 Scenario 2, the electricity generated is able to supply 57.6% of the STP power demand; 40 however, the heat in the exhaust gases is not enough to dry the total amount of dehydrated 41 sludge. 42

In the present research work, different types of biodiesel were produced by a homogeneous alkali transesterification reaction using soybean oil, pork lard, and castor bean oil as raw materials, to evaluate how their different compositions may affect the biodegradability, namely, in the presence of benzene. Biodiesel was characterized according to the European standard EN 14214. The anaerobic biodegradation of the different types of biodiesel was examined as well as its influence on the biodegradation of benzene. Analyses were performed to determine the volume of methane (directly related to the anaerobic biodegradation of bio-diesel), the concentration of benzene over time, and the production of organic acids. The results showed methane production resulting from the anaerobic degradation of all biodiesel types. The differences between the degradation behavior of each fuel were negligible, contrary to what was expected; however, the amount of methane produced was low due to nutrient limitations. This fact was confirmed by the organic acid analysis as well as by the addition of new media. Anaerobic benzene biodegradation was found to be negatively impacted by the presence of all biodiesel types on average; therefore, the results of this study may impact management of sites that contain biodiesel and fuel hydrocarbon contamination.